In an article, published by C. M. Schroeder on pages 91-97 of the January 1978 issue of the Bell System Technical Journal (Vol. 57, No. 1), and entitled "Accurate Silicon Spacer Chips for an Optical Fiber Cable Connector", the author discloses an arrangement for optically splicing two groups of optical fibers by providing for each group a connector comprising a stack of silicon chips. Each chip has on both its sides a set of spaced parallel "V" grooves registering (except for those on the outside stack faces) with the grooves of an adjacent chip to define a plurality of fiber-aligning channels which extend through the stack, and in which channels are received the end sections of the fibers in the corresponding group. The splicing of the fibers in the two groups is effected by butting the two stacks end to end so as to produce as close as possible to an exact alignment between the fibers in one stack and the corresponding fibers in the other.
The mentioned arrangement has been successful in producing optical fiber splices having relatively low loss due to misalignment of the fibers at the splice. The scheme has the deficiencies, however, that, while the use of silicon chips as the carriers for the fiber channel producing "V" grooves permits those grooves to be located on the chip with great accuracy to promote the exact aligning of fibers to be optically spliced, such chips are too costly to lend themselves to extensive commercial use. Moreover such chips are so fragile as to make their use inconvenient in interconnecting optical fibers in the field. Aluminum chips would not have such deficiencies, but the author points out that aluminum chips could not be manufactured repeatedly with the high dimensional accuracy required. Indeed, it is acknowledged in the article that even the silicon chips described therein had thickness variations which were contributions to splice loss.
U.S. patent application, Ser. No. 07/359,453 filed May 31, 1989, now U.S. Pat. No. 4,973,127 in the name Thomas C. Cannon, Jr., Bruce G. LeFevre and Clyde J. Myers (the inventor hereof) and assigned to the assignee hereof, such patent being incorporated by reference herein and made a part hereof, discloses that the aforementioned and other deficiencies can be obviated by providing a two-plug multi-fiber optical connector in which each plug comprises lower and upper synthetic-resinous transversely-spaced juxtaposed guide plates having confronting inner sides in each of which is formed a set of parallel smaller grooves and a pair of larger grooves on laterally opposite sides of that set. The smaller grooves in the two plates of each plug register to define a plurality of channels through that plug in which are received sections of corresponding optical fibers fed into the plug to terminate at ends of the fibers at the front of the plug. A pair of larger grooves in the two plates of each plug likewise register to define a pair of channels in each plug for reception in each channel of an aligning pin. A pair of such pins are, in the use of the connector, inserted with a playless fit partly in such channels of one of such plugs and partly in such channels of the other. The inserted pins align the pair of plugs front-to-front, so precisely that corresponding fiber ends in one and the other of the plugs are optically spliced together with very little loss ensuing at the splice. Because the alignment of the plugs is effected by pins playlessly contacting the plugs at or near their respective transverse center planes at or near which the fiber ends are also located (rather than contacting such plugs at their transversely outer sides), misalignment of the plugs due to variations from normal in the thickness of their plates is avoided, and the transverse alignment between plugs of the ends of the fibers included therein is rendered largely or entirely independent of such thickness variations.
The optical connector which is the subject of the aforementioned Cannon et al patent is, however, disclosed therein as being partly fabricated by the use of a crib fixture employed to implement insertion into each of the two plugs of the connector of the several optical fibers in each of the two groups of such fibers which respectively correspond to, and are terminated by, that plug. Such crib fixture is not, however, well adapted for use in the field. Moreover, in the connector of the Cannon et al patent, the two plugs of the connector are coupled together only through the two aligning pins commonly received therein, and such connector does not include means for preloading the plugs with force operable in the assembled connector to continuously keep the respective fronts of the two plugs in yieldable pressure contact.